Rabu, 30 April 2008

ETOPS/LROPS

ETOPS is an acronym for Extended-range Twin-engine Operational Performance Standards, an International Civil Aviation Organization (ICAO) rule permitting twin-engined commercial air transports to fly routes that, at some points, are farther than a distance of 60 minutes flying time from an emergency or diversion airport with one engine inoperative. ETOPS is also known in the air transport industry by the tongue-in-cheek backronym Engines Turn or Passengers Swim.

This rule allows twin-engined airliners—such as the Airbus A300, A310, A320, A330 and A350 families, and the Boeing 737, 757, 767, 777 and 787 and Tupolev Tu-204 —to fly long distance routes that were previously off-limits to twin-engined aircraft. Contrary to popular/mistaken belief, ETOPS operation has no direct correlation to water, nor distance over water. It refers strictly to single-engine flight times between suitable diversion airfields; regardless as to whether such fields are separated by water, deserts, polar expanses, recurrent (i.e. night-time) airport closures, etc.

ETOPS may be replaced by a newer system, referred to as LROPS, an acronym for Long Range Operational Performance Standards, which will affect all civil airliners, not merely those with a twin-engine configuration. Government-owned aircraft (including military) do not have to adhere to ETOPS. Until the mid-1980's, the term EROPS (extended range operations) was used before being superseded by ETOPS usage.

History

The first direct transatlantic crossing was made in 1919, by John Alcock and Arthur Brown, in a twin-engined Vickers Vimy. It had taken sixteen hours. Due to the unreliability of piston engines at the time, long distance flight using twin engines was considered very risky. A flagship of the piston era, the four-engined Lockheed Constellation airliner, was often jokingly dubbed "the most reliable three-engined airplane flying".[citation needed] Four engines was seen as a must for flight over long distances and inhospitable terrain, or over the ocean.

In 1953 the US Federal Aviation Administration, having recognized piston engine limitations, introduced the "60-minute rule" for 2-engine aircraft. This rule stated that the flight path of twin-engined aircraft should not be further than 60 minutes' flying time from an adequate airport. This forced these aircraft, on certain routes, to fly a dogleg path to stay within regulations; they were totally excluded from certain routes due to lack of en-route airports. The "60-minute rule" was also called the "60-minute diversion period". The totally excluded area was called the "exclusion zone".

Early turbine engine experience

Turbine engines such as the Pratt & Whitney JT8D series in the 1950s and 1960s demonstrated that they had much higher thrust and reliability than any then available piston engines. It was then powering the 2-engined Boeing 737 series and 3-engined Boeing 727. Because of its excellent record, the "60-minute rule" was waived, in 1964, for 3-engined aircraft. This opened the way for the development of wide-body intercontinental trijets such as the Lockheed Tristar and DC-10. By then only 2-engined jets were restricted by the "60-minute rule".

Early twin-engine high-bypass turbofan airliners

Outside the USA, other countries followed ICAO regulations, which allowed for 90 minutes' diversion time. This fact was exploited by Airbus, launching the world's first twin-engined high-bypass turbofan engine Wide-body airliner, the Airbus A300, in 1974. It was about three quarters the size of DC-10s and Tristars and for an equivalent load for the same distance was cheaper to operate.

As a result, twin-engined aircraft like the A300, Boeing 737 and 767 became very popular alternatives to three and four-engined aircraft.

Early ETOPS experience

All the developments in aircraft technologies led the FAA and the ICAO to conclude that it is safe for a properly designed twin-engined airliner to conduct intercontinental transoceanic flights. The guidelines issued form the ETOPS regulations.

The FAA was the first to approve ETOPS guidelines in 1985. It spelled out conditions that need to be fulfilled for a grant of 120 minutes' diversion period, which is sufficient for direct transatlantic flights. Today, ETOPS forms the bulk of transatlantic flights.

ETOPS extensions

In 1988, the FAA amended the ETOPS regulation to allow the extension to 180 minutes diversion period subject to stringent technical and operational qualifications. This made 95% of the earth's surface available to ETOPS flights. The first such flight was conducted in 1989. This set of regulations was subsequently adopted by the Joint Aviation Authorities (JAA), ICAO and other regulatory bodies worldwide.

In this manner the B737, 757 and 767 series, the Airbus A300-600, 310, 320 and 330 series were approved for ETOPS operations. The success of ETOPS aircraft like 767 and 777 killed the intercontinental trijets. This ultimately led Boeing to end the MD-11 program a few years after Boeing's merger with McDonnell Douglas, as well as to scale down the production of its own Boeing 747.

The North Atlantic airways are the most heavily utilized oceanic routes in the world. Most are conveniently covered by ETOPS-120min rules, removing the necessity of utilizing 180-min rules. However, many of the North Atlantic diversion airports, especially those in Iceland and Greenland, are frequently subject to adverse weather conditions making them unavailable for use. As the 180-min rules is the upper limit, the JAA has given 15% extension to the 120-min rules to deal with such contingencies, giving the ETOPS-138min thereby allowing ETOPS flights with such airports closed.

Early ETOPS

The regulations allow an airliner to have ETOPS-120 rating on its entry into service. ETOPS-180 is only possible after 1 year of trouble-free 120-min ETOPS experience. Boeing has convinced the FAA that it could deliver an airliner with ETOPS-180 on its entry into service. This process is called Early ETOPS. Thus the B777 was the first aircraft to carry an ETOPS rating of 180-min at its introduction.

The JAA, however disagreed and the Boeing 777 was rated ETOPS-120 in Europe on its entry into service. European airlines operating the 777 must demonstrate 1 year of trouble-free 120-min ETOPS experience before obtaining 180-min ETOPS for the 777.

ETOPS exclusions

Private jets are exempted from ETOPS by the FAA, but are subject to the ETOPS-120 minute rule in JAA's jurisdiction. Several commercial airline routes are still off-limits to twinjets because of ETOPS regulations. They are routes traversing the South Pacific (e.g. Auckland - Santiago, Chile), Southern Indian Ocean (e.g. Perth, Western Australia - Johannesburg) and Antarctica.

Beyond ETOPS-180

Effective February 15, 2007, the FAA ruled that US-registered twin-engined airplane operators can fly over most of the world other than the South Polar Region, a small section in the South Pacific, and the North Polar area under certain winter weather conditions provided that the inflight shutdown rate is 1 in 100,000 engine hours. This limit is more stringent than ETOPS-180 (2 in 100,000 engine hours).

The qualified aircraft must have appropriate fire-suppression systems, adequate oxygen supplies for crew and passengers (to continue high altitude flight) in the event of depressurisation, and automated defibrillators. Weather reporting, training, and diversion accommodation requirements remain unchanged. Since aircraft occasionally divert for non-engine mechanical problems or passenger medical emergencies, the rule requires that airplane systems be able to support lengthy diversions in remote and sometimes harsh environments. The rules do not apply to 3- or 4-engined cargo aircraft and freed twinjets from ETOPS constraints.

EASA distinguishes between twin-engine (ETOPS) and aircraft with 3 or 4 engines. Rules governing such aircraft (3 or 4 engines) are covered under LROPS rules. LROPS would demand similar rules with regard to emergency oxygen and fire-suppression. EASA is expected to release rules for ETOPS and LROPS in 2008.

ETOPS ratings

The following ratings are awarded under current regulations according the capability of the airline:

  • ETOPS-75
  • ETOPS-90
  • ETOPS-120/138
  • ETOPS-180/207

However, ratings for ETOPS type approval are fewer. They are:

  • ETOPS-90, which keeps pre-ETOPS Airbus A300B4 legally operating under current rules
  • ETOPS-120/138
  • ETOPS-180/207, which covers 95% of the earth's surface.

Approval for ETOPS

ETOPS approval is a two-step process.

Firstly : the airframe and engine combination must satisfy the basic ETOPS requirements during its type certification. This is called ETOPS type approval. Such tests may include shutting down an engine and flying the remaining engine during the complete diversion time. Often such tests are performed in the middle of the oceans. It must be demonstrated that, during the diversion flight, the flight crew is not unduly burdened by extra workload due to the lost engine and that the probability of the remaining engine failing is extremely remote. For example, if an aircraft is rated for ETOPS-180, it means that it should be able to fly with full load and just one engine for 3 hours.

Secondly : An operator who conducts ETOPS flights must satisfy his own country's aviation regulators about his ability to conduct ETOPS flights. This is called

ETOPS operational certification and involves compliance with additional special engineering and flight crew procedures on top of the normal engineering and flight procedures. Pilots and engineering staff must be specially qualified and trained for ETOPS. An airline with extensive experience operating long distance flights may be awarded ETOPS operational approval immediately, others may need to demonstrate ability through a series of ETOPS proving flights.

Regulators closely watch the ETOPS performance of both type certificate holders and their affiliated airlines. Any technical incidents during an ETOPS flight must be recorded. From the data collected globally, the reliability of the particular airframe-engine combination is measured and statistics published. The figures must be within limits of type certifications. Of course, the figures required for ETOPS-180 will always be more stringent than ETOPS-120. Unsatisfactory figures would lead to a downgrade, or worse, suspension of ETOPS capabilities either for the type certificate holder or the airline.

1 komentar:

jfmarcelo mengatakan...

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donde encontrarás los enlaces de todos mis blogs.
UN SALUDO.